1. Field of the Invention
The present invention relates to cutting by means of a rotating axially moving tool, and, more particularly, the invention is a boring tool especially adapted for use in a limited space such as the boring of holes in building plates from a position in the attic of a frame building.
2. Description of the Prior Art
In installing electrical conduits in buildings already constructed, it is customary to bring the conduit into the upper portion or attic of the structure by passing the conduit between the walls of the building and up through the building plates adjacent the roof structure. The space available for working in this attic area is extremely restricted due to the regularly spaced roof rafters and corresponding ceiling joists adjacent the building plates. The difficulties are particularly acute when the roof of the building has a relatively flat pitch or when the roof is supported by closely spaced prefabricated trusses, as typical of many modern building designs. Conventional general purpose drilling devices, even when equipped with flexible cable attachments, have been inconvenient and inadequate for these purposes.
Special plate boring devices have been devised by J. G. Broussard and G. D. Medlin, as disclosed in U.S. Pat. Nos. 3,006,223 and 4,184,795, issued Oct. 31, 1961, and Jan. 22, 1980, respectively. Broussard's device is merely a guide means mountable upon the building plates for receiving and guiding a conventional flexible cable fitted to an electric drill. Medlin's device is simply a rigid tubular extension and angular drive head for use with a portable electric drill. These prior art devices are best suited to non-vertical boring and are not able to penetrate thick building plates when the hollow area of the exterior wall is narrow or when the pitch of the roof is extremely flat. Further, the electric drill or other power source of the prior art devices must be manually advanced by the operator to cause the boring tool to penetrate the building plates. Alignment of these devices, particularly due to the moving nature of the power source, is inconvenient.
Accordingly, it is an object of the present invention to provide an improved boring tool which is particularly suited to drilling vertical access holes in building plates, which is convenient to align from a position distant from the building plates, which is self-feeding, and which does not require advancing of the power source.